Progress Made Towards Resolving the 'Missing Satellites Problem'

Simulations considering the distribution of matter in the Universe suggest that low-mass dwarf galaxies should far out number those of the spiral form and the latter. However, these suggestions have traditionally not aligned with observation leading some to believe that the simulations are wrong. This is known as the 'missing satellites problem'.

For instance, one simulation predicted upwards of 500 dwarf galaxies orbiting our Milky Way alone; Although observations have only been able to recover 11 thus far.  A possible solution to this problem is, of course, that the dwarf galaxies are simply too faint to see. This solution is supported in a recent discovery made by an astronomy team led by Roberto Munoz and Thomas Puzia of Pontificia Universidad Catolica de Chile. The team used a Dark Energy Camera (DECam) on the 4-meter Blanco telescope at Cerro Tololo Inter-American Observatory (CTIO). The analysis revealed a great number of faint, low surface brightness brown dwarf galaxies in the Fornax Cluster. This discovery may vindicate the computer simulations as well as basic ideas surrounding the nature of dark matter. Future studies may uncover a similar distribution of dwarf galaxies orbiting our own Milky Way.

Sources:
http://www.scientificamerican.com/article/milky-way-satellite-dwarf-galaxies/
http://www.astronomy.com/news/2015/11/oodles-of-faint-dwarf-galaxies-in-fornax-shed-light-on-a-cosmological-mystery
https://en.wikipedia.org/wiki/Dwarf_galaxy_problem

Smallest Exoplanet to Exhibit Rayleigh Scattering

Astronomer's from the Las Cumbres Observatory Global Telescope (LCOGT) has observed Rayleigh scattering on the Neptune sized planet known as GJ 3470b. The planet orbits a Red Dwarf star and is 100 light years away, minuscule by astronomical standards. The finding is not only significant because it is the smallest exoplanet for which Rayleigh scattering has been demonstrated but also because measurements indicate a thick-hydrogen rich atmosphere beneath the blue haze. But the most significant detail of this discovery is the tools that's were used; It is the first unambiguous spectroscopic feature in the an exoplanet's atmosphere to be done with small telescopes which are 1-2 meters in diameter. This discovery demonstrates the utility of small telescopes which may help reduce the cost-to-data ratio of astronomical endeavors in the future.

Sources:
http://arxiv.org/abs/1511.05601
https://astronomynow.com/2015/11/27/a-blue-neptune-sized-exoplanet-around-a-red-dwarf-star/

Earth's Dark Matter Filaments

A new study published by Gary Prezeau of NASA's Jet Propulsion Laboratory reveals that Earth may have long, narrow filaments of dark matter emanating from it. According to Prezeau's results, these "hairs" form when Earth's gravity focuses streams of dark matter particles. If this proposal is indeed correct, large sources of dark matter may be closer than previously thought. Pinpointing the exact location of these filaments could lead to a successful detection of dark matter particles, a detection that has eluded scientists for over 30 years.


Sources:
 http://www.universetoday.com/123583/earth-may-be-hairy-with-dark-matter/
https://en.wikipedia.org/wiki/Dark_matter

Galactic Heartbeats

When giant red stars approach the end of their life an epic tug-of-war becomes evident. The outward force from pressure begins to overcome the inward force from gravity. After expanding to a certain volume,  activity decreases in the star and the outward force from pressure decreases. That is, gravity begins to overcome. This oscillatory phenomenon effectively changes the star's luminosity thus causing it to pulsate in brightness.

This cycle was thought to be imperceivable in other galaxies due to luminosity averaging from the light of other, steady, stars. But astronomers at Yale and Harvard have successfully detected such pulsating in a galaxy known as M87. They found that 25 percent of the pixels in the Hubble image increased in brightness periodically. The "heartbeat" of the galaxy is, on average, every 270 days.

One could imagine that this period varies due to millions of old red stars oscillating with different phases. It does seem curious that these pulses are not averaged out to a constant flux. This suggests that a large number of the old red stars must somehow have similar phases. Astronomer Jieun Choi says that their model predicts more dramatic pulsating in younger galaxies and that they hope to discover more examples of this in the future.


Sources:
http://www.scienceworldreport.com/articles/33072/20151116/galaxy-heartbeat-astronomers-find-pulse-distant.htm
https://en.wikipedia.org/wiki/Red_giant

Hubble Captures Lentricular Galaxy

S0 galaxies, also known as Lentricular galaxies, are intermediate between E7 elliptical galaxies and spiral galaxies. Some think S0 galaxies are simply spiral galaxies with faded arms. Alternative speculations take note of the fact that S0 galaxies are typically more luminous than spiral galaxies. This suggests that they might not simply be faded spirals but might have come about from
galaxies merging together.

 The images to the right is a classic example of such a galaxy. From a distance the galaxy appears elliptical in form.
 But upon closer inspection some hints of a spiral structure are observable. The galaxy is known as Markarian 820 and is located 300 million light years from earth. We can see that it's inclination is perfectly positioned to be a well suited candidate for analysis.








Sources:
http://www.sci-news.com/astronomy/science-hubble-markarian820-lenticular-galaxy-03400.html
https://en.wikipedia.org/wiki/Lenticular_galaxy

General Relativity's Final Prediction

In 1915, Albert Einstein published what many consider to be his magnum opus: The General Theory of Relativity (GTR). In this work, Einstein forever changed the way we think about gravity and it's relation to space and time. But GTR makes predictions that go far beyond our familiar conception of gravity. Proven phenomena such as time dilation, gravitational lensing, frame dragging, and even black holes all have their theoretical origins in GTR. Indeed, despite being a century old Einstein's general theory of relativity continues to bare fruit. But there is a final implication of GTR that has yet to be directly detected; An implication that physicists may finally be on the verge of measuring. This final prediction is gravitational waves.

Gravitational waves are essentially ripples in the geometry of spacetime. To create such a wave a mass must be accelerated through space in a particular way such that the quadrupole moment of the mass distribution varies. That is, in order to create ripples of expanding and contracting spacetime a mass must accelerate through space in a non-spherically symmetric and non-cylindrically symmetric fashion.

Unlike waves of the longitudinal form, gravitational waves are what's known as quadrupole waves. Their mode of propagation is the deformation of space itself. This causes objects in their path to expand and contract as the wave passes through them. And it is precisely this property that physicists are trying to detect. In fact, this is the sole objective of the Laser Interferometer Gravitational-Wave Observatory (LIGO).

Founded in 1992 and at a cost of $620 million, LIGO is the largest scientific experiment ever devised with the intent of directly detecting gravitational waves. LIGO is attempting to detect these waves by essentially passing two lasers of the same wavelength through each other but 90 degrees out of phase. Consequently, this creates destructive interference and nothing is observed. If, however, a gravitational wave were to pass through this destructive interference pattern the beams' wavelengths would be altered opposite to each other. This means that the two overlapping lasers would no longer exhibit perfect destructive interference and a signal should be detected.

This set up must be incredibly precise to detect the minuscule effects of gravitational waves. It is estimated that even the strongest sources of gravitational waves would only contract earth's space by a millionth of the width of a proton. Additionally, other disturbances that could affect the system must be carefully weeded out. It may be no surprise then that LIGO's initial run, from 2002-2010, produced no detections.

Rather than being an indictment of GTR,  LIGO's initial detection failure was likely due to insufficient sensitivity. As a result, LIGO shutdown operation for multiple years in order to expand it's capabilities. With improved detectors, the Advanced LIGO has increased it's sensitivity by a factor of 10. Operations began again on September 18th 2015 and it is likely just a matter of time before a direct detection will be made by LIGO.


If successfully detected, gravitational waves could open up an entirely new way of studying astronomical objects. Up until now, astrophysicists' only information regarding the universe has come in the form of light and matter. It is exciting to imagine gravity being added to that list.

Thus, physicists may be on the verge of directly verifying gravitational waves. This will, thereby, further validate General Relativity and may, in time, expand the tools available to astrophysicists.


Sources:
https://ligo.caltech.edu/
https://en.wikipedia.org/wiki/Gravitational_wave
https://en.wikipedia.org/wiki/General_relativity
https://en.wikipedia.org/wiki/LIGO#Advanced_LIGO
http://www.skyandtelescope.com/astronomy-news/advanced-ligo-switches-on-10142015/

In Terms of Life in the Universe, Earth May be Early to the Party.

A new theoretical study finds that 92 percent of planets that could harbor life don't even exist yet. It does seem unusual that the Earth is only one-third the age of the universe. Perhaps, this is not the norm. Perhaps, this study helps explain why the universe isn't bustling with consciousness yet.





Source: http://www.astronomy.com/news/2015/10/most-earth-like-worlds-have-yet-to-be-born-according-to-theoretical-study

When Stars Glitch

Every armchair astronomer is familiar with the concept of violently rotating neutron stars, better known as pulsars. They are, after all, popular celestial objects with unique characteristics. For instance, pulsars are highly magnetized and accompanied by beams of radiation emanating from their magnetic poles. Pulsars have regular periods that causes them to pulse in precise intervals. This pulsing is, in fact, so regular that certain types even rival atomic clocks in terms of their time keeping precision. These facts are well known to a general consumer of popular science. What may be lesser known, however, is that they sometimes glitch.

Occasionally, pulsars have been known to exhibit a sudden, usually temporary change in rotational frequency. This event has been dubbed a glitch. Glitches can be as large as one millionth the usual rotational frequency. Small, but not too small to notice.

After a glitch has been detected, the pulsars typically return to their normal rotational frequency during a finite recovery period. Recovery periods can range from days to years. Though the exact reasons for the glitch can only be speculated at this time, the leading idea is that the pulsar's typically faster rotating internal fluid briefly matches the rotational frequency of the outer crust. In a sense, the two dynamic materials briefly couple. Only to decouple after affecting the star's rotational frequency.

If this hypothesis is indeed correct, it means there is a limit on pulsars' moments of inertia. This, in turn, sets a limit on the stars' mass-radius relation. Specifically, the radius must be greater than or equal to 2.9 * GM/c^2.

In time, pulsar glitches will be better understood and will thereby help to explain why these strange stars look and behave the way that they do. Glitches may also be, one day, added to the list of popular science factoids. This will surely delight armchair astronomers the world over.

Sources:
http://www.nature.com/nature/journal/v359/n6396/abs/359616a0.html
https://en.wikipedia.org/wiki/Pulsar
http://astronomy.swin.edu.au/cosmos/G/Glitch

New Horizons' Next Stop

Several months after New Horizons' historic flyby of Pluto, scientists have decided on the probe's next destination: a Kuiper Belt object (KBO) named 2014 MU69. This will complete the second component of New Horizons' mission; The first, of course, being a survey a Pluto and its associated moons. 

When the interplanetary space probe New Horizons launched in January 2006 one of it's main purposes was to study such objects. These ancient bodies are, in a sense, the remnants of the solar system. Studying their composition could help scientists understand how distant spherical bodies accreted. 

2014 MU69 was discovered in 2014 by the Hubble Space Telescope and met the orbital criteria for New Horizons.  After the Pluto flyby, New Horizons began making a series of trajectory adjustments in August and expects to reach 2014 MU69 in January 2019.  Once it does, the probe will attempt to resolve a series of observational objectives.  These include:

- a geologic survey of the bodies' surface
- a collection of surface data including temperature and composition
- a search for geologic activity 
- a search for any orbiting material

New Horizons' exploration of 2014 MU69 will be the longest distance exploration of a celestial body ever; An exploration that will likely not be replicated for many years. The data New Horizons' collects will help improve scientists' understanding of how the solar system formed while taking some interesting pictures along the way. 



Sources: 
https://en.wikipedia.org/wiki/2014_MU69
https://en.wikipedia.org/wiki/New_Horizons
http://www.skyandtelescope.com/astronomy-news/new-horizons-a-billion-miles-to-2014-mu69-10012015/