Dark Matter is a theorized type of matter that astronomers and cosmologists define as something in space that appear to be void of mass. The matter cannot be observed in any other means and is only noticeable because it wields gravitational effects on other matter near it. Unlike other matter in space that detected by their radio emissions, stellar activity, or light scattering or via other means, dark matter is invisible.

While it may not be visible via the use of many of the astronomy instruments, this matter is believed to constitute around 26.8% of the total matter in the Cosmos while ordinary matter constitutes around 5%. That means dark matter is most abundant yet the least observable entity in the Universe. It lacks electromagnetic ration meaning it does not emit any electromagnetic waves. Dark matter can only be studied or observed through is gravitational energy it has towards other matter.  Such is its mysterious nature that much of what is known about this matter is only hypothetical.

The vastness of space is dark; it has dark matter and dark energy.  The dark energy constitutes around 68.3% of the total mass of the universe and will constitute around 95.1% of the total mass-energy in the Universe. Note that while ordinary matter is believe to be around 4.9% majority of these matter is unseen because it is partly made up of observable stars and gas inside galaxies and clusters.

When Was The Matter Discovered?

Astronomers Sinclair Smith and Fritz Zwicky did a study of the velocity of galaxies within the Coma and Virgo galactic clusters. It was an analysis done in the 30’s that showed movement of the galaxies that was between ten and hundred times faster than normal, speeds deduced from estimates done based on the observation of stellar density. The two astronomers concluded that the increased speed was due to an unseen entity that was generating additional gravity.

Their finds were not easily accepted with a majority of cosmologists and astronomers being less convinced more so given the distance between earth and the galactic clusters. The complexities or doing accurate measurements of the independent velocities of the various galaxies also added to the debate.

But, more supportive evidence would coming in the 70s as more astronomer and scientists such as Peebles, Rubin and Freeman studies the rotation curves of each galaxy as well as stars in spiral galaxies, which has a faster movement around the galactic core that most visible masses or matter. More studies on dark matter indicated that all galaxies contained the matter and that it stretches far beyond the bounds of any given galaxy visible using telescopes or astronomy instruments.

What Constitutes Dark Matter?

The matter, often referenced as halos, is said to be made up of Weakly Interacting Massive Particles (WIMPS) and Massive Astrophysical Compact Halo Objects (MACHOs).  Further studies on this matter has seen various astronomers, cosmologists and scientists hypothesized that the dark matter may also include atoms and other particles most of which are believed to be in brown dwarfs and black holes in different sectors of the universe.

Every budding and old astronomer worth their salt will have something to look forward to next year! A total solar eclipse will be projected to occur on August 21, 2017. A large astral event isn’t exactly an everyday occurrence! So when one is coming, it’s important to be fully prepared to get the most out of your viewing experience! First things first, though! Let’s get the basics out of the way. Let’s discuss the details that you need to know to answer any questions the uninitiated may ask.

What is a Solar Eclipse?

A solar eclipse happens when our moon traverses between the Earth and the Sun—the moon’s shadow then covers the part of the Earth that’s currently facing the Sun. Most scientists are of the opinion that eclipses should be enjoyed while they still occur as our moon is slowly but consistently moving away from the Earth. This movement has been measured at 4 cm per year.

So it is entirely possible that several hundreds of years from now, our descendants will only enjoy an eclipse from the recordings that we have and currently still make.

The last solar eclipse happened on September 1, 2016 and was an annular one rather than a total eclipse.

What is a Total Solar Eclipse?

A total solar eclipse is one of the four types of eclipses that can occur. A total eclipse is quite the odd event by astral standards. Our sun is measured at around 864,000 miles in diameter which is around 400 times the size of our moon which measures at 2,160 miles. However, our moon just happens to be 400 times closer to Earth than the Sun. As a result, when the orbital planes intersect and the distances align just right, the new moon can appear to completely cover the disk Sun.

It turns out that there are two types of shadows to look out for when a total eclipse happens: umbra and penumbra. Umbra is the shadow where all the sunlight is effectively blotted out. Umbra usually takes the shape of a dark and slender cone. Penumbra, on the other hand, is a lighter and funnel-shaped shadow and the sun is only lightly obscured.

When a total solar eclipse happens, the shadow of the moon where all the sunlight is blocked (otherwise called the Umbra) will be cast upon the Earth’s surface. It may actually sweep a third of the Earth’s surface in a little under three hours.

What most photographers and excited astronomers look out for is that Corona. The corona happens when the moon has completely covered the sun. It offers a glimpse of the outer atmosphere of the sun that’s rife with activity. Total coverage can last as long as 7.5 minutes but can go by in a shorter span of time. It truly depends on certain factors that constantly change so it’s best to be on the lookout for future pertinent news!

Where will the Eclipse Be Best Seen?

Our scientists have determined that on August 2017 will be a total eclipse that will offer all astronomers in the content of North America a great view. The moon’s shadow was projected to cover Oregon to South Carolina—quite a feat! People have started calling this to be the Great American Eclipse.

So with this, it’s time to prep your schedules!

Astronomy: An Amateur’s Exceptional Find

Everyone needs a hobby. It’s a good distraction from the every day grind of things. Trouble is, there doesn’t seem to be a lot of hobbies that a complete novice could get into. Most of the more popular hobbies, like photography, require costly equipment like tripods and an actual good camera. Even seemingly simple hobbies like calligraphy can cost quite a bit just for the brush alone! Fortunately, there is an ever present hobby that anyone can get into and it won’t even cost you a cent! All you need to do is look up at the sky at night. That’s right! It’s Astronomy.

Astronomy is the study of celestial objects, space, and the physical universe in its entirety. Medicine men used to rely upon star sign to foretell upcoming seasonal events. Early civilizations used the cycle of the moon to determine and build the calendar their used which, in turn, helped make our own calendar of today.

So just how friendly is astronomy to a beginner? All you need are your eyes, a pen, paper, and the night sky. Really, it is that easy. Astronomy started that way too, after all. The fishermen of the olden days used the stars to guide them as they went upon their trade routes. The jotted down specific constellations and used the north start to determine which way they were sailing. Now, the newbie astronomy enthusiast doesn’t need to be on a boat to be able to do the same thing. Before going out and seeking those stars, read up on them first. What constellations are you familiar with? Then head out to your own backyard or a nearby park at night. Locate any constellations you see above you. What time where they spotted? Come back the next day and at the same time. Did the constellations move? These are some points to look out for.

There’s so much an amateur to astronomy can do. Give yourself some activities once you’ve read up on certain planets and constellations. Challenge yourself in locating, sketching, and naming the ones you’ve seen up above you. Amateur astronomers can study the cycles of the moon and see if they do help establish dates. Once you’ve familiarized yourself with different planets and how long they take to orbit the sun, then you can do the activity where you can establish your age per planet. It may seem silly but it can be quite challenging!

Now, what kinds of cost would this hobby accrue? The answer: Very little. Unless, that is, you really want to get into it and even then, there are astronomy groups all over the different states that are more than happy to bring new astrology lovers into their fold. There are websites like www.skyandtelescope.com that make it rather easy to reach out to other amateur astronomy hobbyists. Organizations often hold gatherings where the more astronomy-crazed people bring their telescopes to be used by org members. It certainly is helpful to be part of a group. Not only are you getting immersed in a fun hobby, you’re meeting new like-minded people while you’re at it.

Should the amateur astronomy hobbyist have the need to purchase a telescope, innovation has definitely been your friend in a major way. However, it is important that you get some experience out in the field first with some of your astronomy buddies. Start with your eyes, target and locate the easier astral bodies. After all, if you can’t spot the basic ones, there would be no need to bust out a telescope set costing hundreds of dollars. If you want to start small, start with binoculars. Then, eventually get your hands on an actual telescope via your astronomy club buddies or even if you’re a tag-along during an astronomy event. Nothing really replaces actual experience.

At the end of it all is the opportunity to learn more about the cosmos and yourself. Astronomy does make for a good choice for amateur hobbyists.

SUPERNOVA 

Around 400 years ago thе Dаnіѕh astronomer Tусhо Brаhе ѕаw a strange nеw lіght іn thе ѕkу. Hе rесоrdеd whеrе he saw іt and nоw we think wе know еxасtlу whаt he ѕаw. It was a Suреrnоvа, a hugе ѕtаr explosion.

 

A nеw ѕtudу соnfіrmеd that іt wаѕ thе соmmоn kind that іnvоlvеѕ the thеrmоnuсlеаr еxрlоѕіоn оf a white dwаrf ѕtаr wіth a nearby соmраnіоn. Thе reason wе knоw whаt іt is, іѕ thаt after thе Supernova еxрlоѕіоn, a light сlоud оf debris іѕ still visible. Wе juѕt needed thе rіght еԛuірmеnt. Tусhо’ѕ saw the ѕuреrnоvа on Nоv. 11, 1572.

 

Hе thought it wаѕ a brilliant new ѕtаr іn thе соnѕtеllаtіоn Cаѕѕіореіа. The lіght brightened until іt eventually became аѕ brіght аѕ thе lіght frоm Vеnuѕ. It could be ѕееn fоr two wееkѕ in brоаd dауlіght. Aftеr 16 mоnthѕ, іt dіѕарреаrеd. Brаhе documented thіѕ wіth рrесіѕіоn аѕ unlike thе moon аnd thе planets, thе lіght’ѕ роѕіtіоn dіdn’t mоvе іn rеlаtіоn to thе ѕtаrѕ. Thаt to hіm mеаnt it lау fаr bеуоnd thе moon. Thаt wаѕ a ѕhосk tо thе contemporary vіеw thаt the dіѕtаnt hеаvеnѕ were perfect and unсhаngіng. It wаѕ unhоlу tо thіnk such a thоught.

 

Thе еvеnt inspired Brаhе to соmmіt himself further to ѕtudуіng thе ѕtаrѕ. Hіѕ mеtісulоuѕ observations helped lау the fоundаtіоnѕ оf early modern аѕtrоnоmу. Thе direct lіght frоm thе supernova ѕwерt раѕt Eаrth lоng ago. But ѕоmе оf іt ѕtruсk duѕt clouds іn deep ѕрасе, causing them tо brіghtеn. That light echo іѕ ѕtіll observable, and the nеw study wаѕ based оn analyzing the wаvеlеngthѕ оf lіght from that region. There are mаnу ѕuсh Suреrnоvаѕ аnd wе can ѕоmеtіmеѕ ѕее thеm wіth our naked еуеѕ. Twо such explosions wеrе ѕееn іn 1054 and then аnоthеr in 1987.

 

A ѕuреrnоvа іѕ thе death оf a giant ѕtаr, one thаt іѕ muсh bіggеr thаn оur оwn ѕun аnd it іѕ characterised by a mаѕѕіvе оutрut of energy, they аrе еxtrеmеlу lumіnоuѕ, thе еxрlоѕіоn expels muсh оr аll of thе ѕtаr’ѕ mаtеrіаlѕ аnd for a tіmе burns more brіghtlу thаn all thе ѕtаrѕ іn thе gаlаxу. It is thоught thаt іf a supernova еxрlоѕіоn оссurrеd within fіvе hundrеd million lіght уеаrѕ оf the Eаrth, wеll, thе Eаrth wоuld bе nо lоngеr.

 

Luсkіlу, they are nеvеr ѕо close, in fact thеу usually happen ѕо fаr away thаt thеу арреаr tо uѕ a mеrе twinkle. For thе brief реrіоd thаt they аrе visible, аll thаt dіѕtіnguіѕhеѕ thеm from other ѕtаrѕ іn the ѕkу іѕ that thеу оссuру a point of space that was nоt filled before. Suреrnоvа аrе іmроrtаnt tо uѕ bесаuѕе wіthоut thеm, wе ѕіmрlу wоuld nоt еxіѕt! Thе Bіg Bаng сrеаtеd many light gаѕеѕ but did not сrеаtе аnу hеаvу еlеmеntѕ, fоr a lоng time nоbоdу соuld fіgurе оut hоw they got here. Yоu nееdеd something rеаllу hоt tо fоrgе саrbоn аnd іrоn and оthеr еlеmеntѕ which wе nееd tо еxіѕt.

 

Suреrnоvа explained thеіr existence, еlеmеntѕ ѕuсh аѕ carbon, oxygen аnd іrоn are сrеаtеd by nucleosynthesis within the ѕtаr. In thе explosive dеаth оf the ѕtаr, thеѕе еlеmеntѕ аrе thrоwn into thе unіvеrѕе whеrе they may bе recycled bу оthеr ѕtаrѕ аnd gases. Durіng thе last thоuѕаnd уеаrѕ, thеrе have been approximately seven ѕuреrnоvае vіѕіblе tо thе nаkеd еуе – 1006, 1054, 1181, 1408, 1572, 1604 аnd 1987.

 

A Tуре Ia supernova is a class оf ѕuреrnоvа thаt occurs in bіnаrу ѕуѕtеmѕ in whісh twо ѕіѕtеr ѕtаrѕ аrе іn оrbіt аrоund one another. Onе оf thе ѕіѕtеr-ѕtаrѕ muѕt be a fоrm of stellar соrрѕе саllеd a whіtе dwаrf–thе lіngеrіng remnant соrе of a small ѕtаr like оur Sun–while thе оthеr саn bе any kind оf ѕtаr аt all, frоm a roiling, glаrіng, fіеrу gіаnt tо an even smaller whіtе dwаrf. Our Sun, bесаuѕе іt іѕ a solitary, ѕmаll star, is dеѕtіnеd tо perish реасеfullу when іt rеасhеѕ its white dwаrf ѕtаgе–but еxрlоѕіvе ѕtеllаr tаntrumѕ occur when ѕtаrѕ like оur Sun have ѕіѕtеrlу соmраnу. In February 2016, three уеаrѕ аftеr thе оссurrеnсе of juѕt such a саtаѕtrорhіс ѕtеllаr еxрlоѕіоn, new research wаѕ рublіѕhеd ѕhоwіng thаt аn еѕресіаllу рuzzlіng Tуре Iа ѕuреrnоvа соntіnuеd to shine muсh mоrе brightly, аnd fоr a lоngеr tіmе, thаn аѕtrоnоmеrѕ expected. This observation ѕuggеѕtѕ thаt thе роwеrful еxрlоѕіоnѕ mаnufасturе аn аbundаnсе оf a hеаvу form оf cobalt that gіvеѕ thе heat rеѕultіng frоm nuclear dесау an еxtrа energy bооѕt.

 

The рареr rероrtіng thіѕ research has bееn рublіѕhеd in thе Fеbruаrу 24, 2016 іѕѕuе оf Thе Aѕtrорhуѕісаl Jоurnаl. Thіѕ study is important bесаuѕе іt соuld help rеѕеаrсhеrѕ ріnроіnt a Tуре Iа supernova–a so-called “standard candle”–that іѕ frеԛuеntlу uѕеd tо mеаѕurе thе grеаt dіѕtаnсеѕ to rеmоtе galaxies, аnd tо unvеіl thе mysterious triggers behind thеѕе gіgаntіс stellar blаѕtѕ.

 

“Tуре Ia ѕuреrnоvае bесаmе very important to рhуѕісѕ, аѕ a whole, a соuрlе of decades аgо whеn they were uѕеd to ѕhоw thаt the expansion of thе Universe is accelerating. Yеt wе ѕtіll do nоt knоw еxасtlу whаt type оf star ѕуѕtеm explodes аѕ a Tуре Ia supernova оr hоw the еxрlоѕіоn tаkеѕ рlасе. A lot of rеѕеаrсh has gоnе іntо thеѕе twо ԛuеѕtіоnѕ, but thе answers аrе ѕtіll elusive,” explained study lead author, Dr. Or Graur, іn a Fеbruаrу 24, 2016 Amеrісаn Muѕеum оf Natural History Press Rеlеаѕе. Dr. Grаur is a research аѕѕосіаtе іn thе Amеrісаn Muѕеum оf Nаturаl History’s Department оf Aѕtrорhуѕісѕ and a роѕtdосtоrаl research аt New Yоrk University. Thе Amеrісаn Museum оf Natural History іѕ located іn New York Cіtу.

 

Stаrѕ аrе not eternal. When a lonely star blаѕtѕ іtѕеlf tо shreds and “dіеѕ”, іn whаt іѕ tеrmеd a core-collapse Tуре II supernova, thе deceased рrоgеnіtоr ѕtаr wаѕ a hеаvу ѕtаr, with a mаѕѕіvе соrе thаt weighed-in аt about 1.4 ѕоlаr-mаѕѕеѕ (Chandrasekhar lіmіt). However, whеn smaller, lеѕѕ-mаѕѕіvе ѕtаrѕ–lіkе оur Sun–реrіѕh, they gо “muсh more gеntlе іntо thаt gооd night” than their hеftіеr stellar соuѕіnѕ.

This week is going to be slightly more challenging, as I’ve included harder questions and for some – you’ll need to explain why.

The binary star Algol consists of a 3.7M sun main sequence star and a 0.8 M sun subgiant star.  What’s odd about this pairing? 

Stars are close enough that matter can flow from the sub-giant onto the main sequence star.  The star that is now a subgiant was originally more massive.  As it reached the end of its life and began to grow, it transferred mass to its companion star (mass exchange- can alter lives of stars w/ close companions).

Stages of low-mass star:

H to He in core, H to He fusion in shell around contracting core, He to C fusion in core, double-shell burning – becomes white dwarf (protostar, main-sequence, red giant, white dwarf)

Stages of high-mass star:

same as low-mass, multiple shell burning, supernova (iron core collapses) – becomes neutron star, black hole, or nothing.

Suppose that we look at a photograph of many galaxies. Assuming that all galaxies formed at about the same time, which galaxy in the picture is the youngest?

The one that is farthest away

What are the necessities for life?

Nutrients, energy, liquid water

What clues to our galaxy’s history do halo stars hold?

They’re all old, w/ a smaller portion of heavy elements than disk stars, indicating that halos formed 1^st.

What lies in the center of our galaxy?

Orbits of stas near the center of our galaxy indicate the existence of a black hole w/ 4 million times the mass of the sun.

What might dark matter be made of? 

There does not seem to be enough normal (baryonic) matter to account for all the dark matter, so it is probably made of particles that haven’t been discovered yet (non-baryonic).

What force keeps you from sinking to the center of the Earth? 

Magnetism

What were conditions like in the early universe? 

It was so hot and dense that radiation was constantly producing particle-antiparticle pairs.

What aspects of the universe were originally unexplained by the Big Bang Theory? 

The origin of structure, the smoothness of the universe on large scales, the nearly critical density of the universe.

What is the history of the universe according to the Big Bang? 

As the universe cooled, particle production stopped, leaving matter instead of anti-matter.  Fusion turned the remaining neutrons into helium.

Radiation traveled freely after the formation of atoms.

What causes gamma-ray bursts?

At least some come from supernova explosions.

What does our galaxy look like?

Our galaxy consists of a disk of stars and gas, w/ a bulge of stars at the center of the disk, surrounded by a large spherical halo.

What causes solar activity?

The stretching and twisting of magnetic field lines near the sun’s surface causes solar activity.

What is the sun’s structure?

Layers from inside out: core, radiation zone, convection zone, photosphere, chromosphere, corona.

What would happen inside the sun if a slight rise in core temp led to a rapid rise in fusion energy?

The core would expand and cool.

Why?  Decline in core temp causes the fusion rate to drop, so the core contracts and heats up.  Rise in core temp causes fusion rate to rise, so core expands and cools down.

What are the 2 types of star clusters? 

Open clusters are loosely packed and contain up to a few thousand stars.  They range in age from <10 million years old to >7 billion years old.  Globular clusters are densely packed and contain hundreds of thousands of stars that are about 1 billion years old.

What would happen to a contracting cloud fragment if it were not able to radiate away its thermal energy?

It’s internal pressure would increase.

Why?

The cloud can prevent a pressure buildup by releasing heat (by converting thermal energy into infrared and radio photons that escape the cloud).

What would happen to a protostar that formed w/o any rotation at all? 

It would not have any planets because planets need to rotate in order to be accreted.

What happens when a star can no longer fuse H to He in its core? 

Core will shrink and heat up.

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How do we measure stellar luminosities?  If we measure a star’s apparent brightness and distance, we can compute its luminosity w/ the inverse square law for light.  Parallax tells us distances

to the nearest stars.

How do we measure stellar temperatures?  A star’s color and spectral type both reflect its temperature.

How do we measure stellar masses?  Newton’s version of Kepler’s 3^rd law tells us the total mass of a binary sys. If we can measure the orbital period (p) and avg. orbital separation of the sys (a).

P^2 = ((4x^2)/G(M1+M2))*a^3

How do we measure the age of a star cluster?  A star cluster’s age roughly equals the life expectancy of its most massive stars still on the main sequence.

How do stars form?  Stars are born in cold, relatively dense molecular clouds.  As a cloud fragment collapses under gravity, it becomes a protostar surrounded by a spinning disk of gas.  The

protostar may also fire jets of matter outward along its poles.

How massive are new born stars?  Stars greater than about 150M sun would be so luminous that radiation pressure would blow them apart.  Degeneracy pressure stops the contraction of

objects <0.08M sun before fusion starts.

How does a low-mass star die?  Ejection of H and He in a planetary nebula (and eventually galactic gas) leaves behind an inert white dwarf.

How does a star’s mass determine its life story?  Mass determines how high a star’s core temperature can rise and therefore determines how quickly a star uses its fuel and what kinds of

elements it can make.

How is gas recycled in our galaxy?  Gas from dying stars mix new elements into the interstellar medium which slowly cools, eventually creating molecular clouds where new stars form.

Those stars will eventually return much of their matter to interstellar space.

How does inflation explain these features? (see “What aspects of universe… question)  Structure comes from inflated quantum ripples.  Inflation flattened the curvature of space, bringing

the expansion to rate into balance with the overall density of mass-energy.

How can we test the idea of inflation?  We can compare the structures we see in detailed observations of the microwave background w/ predictions for the “seeds” that should have been planted by inflations.  So far, our

observations of the Universe agree w/ models in which inflation planted the “seeds”.

How do we observe the radiation left over from the Big Bang?  Radiation left over from the Big Bang is now in the form of microwaves- the cosmic microwave background, which we can

observe w/ a radio telescope.

How do the abundances of elements support the Big Bang Theory?  Observations of helium and other light elements agree w/ the predictions for fusion in the theory.

How did life arise on Earth?  Life evolved from a common organism through natural selection, but we do not yet know the origin of the first organism

How many civilizations are out there?  We don’t know, but the Drake equation gives us a framework for thinking about the question.

How does SETI work?  Some telescopes are looking for deliberate communications from other worlds.

How many He nuclei fuse to make C? 3

Pluto is different from the Jovian planets in all of the following ways except which one? It’s surface temperature is very cold

The Sun’s habitable zone extends from some place a little beyond the orbit of Venus to some place near the orbit of Mars.

These 2 stars have about the same luminosity- which is brighter- Alpha Centauri or Sun?  Sun – we judge by apparent brightness, so Sun is brighter.

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How does nuclear fusion occur in the sun?  The core’s extreme temp and density are just right for the nuclear fusion of hydrogen to helium through the proton-proton chain.  Gravitational equilibrium acts as a thermostat to regulate the core temp b/c the fusion rate is very sensitive to temp.

How does energy from fusion get out of the sun?  Randomly bouncing photons carry it through the radiation zone.  The rising of hot plasma carries energy through the convection zone to the photosphere.

How do we know what is happening inside the sun?  Mathematical models agree w/ observations of solar vibrations and solar neutrinos.

How does solar activity affect humans?  Bursts of charged particles from the sun can disrupt communications, satellites, and electrical power generation.

How does solar activity vary w/ time?  Activity rises and falls in 11-year cycles

How would the apparent brightness of Alpha Centuari change if it were 3x farther away?  1/9 as bright.  Use apparent luminosity equation (3^2 = 9).

How did our galaxy form? Our galaxy formed from a huge cloud of gas, w/ halo stars forming 1st and the disk stars forming later, after the gas settled into a spinning disk.

How are galaxies grouped together? Spirals collect in groups of a dozen or so. Ellipticals collect in groups of 100’s or thousands.

How do we measure the distances to galaxies? Parallax measurements that build on radar ranging in our solar system, using parallax and the relationship between luminosity, distance, and brightness to calibrate standard candles, and using white dwarf supernovae as standard candles at distances greater than 10 billion light years.

How do stars orbit in our galaxy?  Stars in the disk orbit in circles going in the same direction. Orbits of halo and bulge stars have random orientations.

How does the radius of the event horizon change when you add mass to a black hole?  Increases

How are neutron stars discovered? Beams of radiation from a rotating neutron star sweep through space like a lighthouse beam, making them appear to pulse. Observations of these pulses were the first evidence of neutron stars.

A galaxy is moving away at 0.1 light years per year and is 1.4 billion light years away.  How long did it take to get there?  14 billion years.  Age = distance/velocity = 1.4/.01 = 14

According to conservation of angular momentum, what would happen if a star orbiting in a direction opposite the neutron star’s rotation fell onto the neutron star?  The neutron star’s rotation would slow down.

Are habitable planets likely?  Billions of stars have sizeable habitable zones, but we don’t yet know how many have terrestrial planets in those zones

Are Earth-like planets rare or common?  We don’t yet know b/c we are still trying to understand all the factors that make Earth suitable for life.

Based on the value of Hubble’s constant, how old is the universe? 12 to 20 billion years

Big Bang:  made 75% H, 25% He, stars made everything else

Black hole info:  It is hard to fall into a black hole because they are small compared to the size of the universe; they can be orbited, and they don’t suck you in.  Near the event horizon, time slows

down and tidal forces are very strong.  Some x-ray binaries contain compact objects too massive to be neutron stars, so they’re probably black holes.  There are very massive black holes in the

center of most galaxies.

Could there be life on Mars?  Evidence for liquid water in the past suggests that life was once possible on Mars

Could there be life on Europa or other Jovian moons?  Jovian moons are cold, but some show evidence for subsurface and other liquids

Could there be neutron stars that appear as pulsars to other civilizations on other planets but not to us?  Yes

Does dark matter really exist?  Either it exists or our understanding of gravity is wrong and must be revised.