The universe suddenly looks a lot more crowded…
We already estimated that there were about 100 billion galaxies in the observable universe, but new research shows that this estimate is at least 10 times too low!
First, what is the observable universe? Well, it is the most distant part of the universe we can see from Earth because, in theory, the light from these objects have had time to reach Earth.
In a new study using surveys taken by the Hubble Space Telescope and other observatories, astronomers came to the surprising conclusion that there are at least 10 times more galaxies in the observable universe than previously thought. This places the universe’s estimated population at, minimally, 2 trillion galaxies!
The results have clear implications for galaxy formation, and also helps shed light on an ancient astronomical paradox – why is the sky dark at night?
Most of these newly discovered galaxies were relatively small and faint, with masses similar to those of the satellite galaxies surrounding the Milky Way.
Using deep-space images from the Hubble Space Telescope and other observatories, astronomers converted the images into 3-D, in order to make accurate measurements of the number of galaxies at different epochs in the universe’s history.
In addition, they used new mathematical models, which allowed them to infer the existence of galaxies that the current generation of telescopes cannot observe. This led to the surprising conclusion that in order for the numbers of galaxies we now see and their masses to add up, there must be a further 90% of galaxies in the observable universe that are too faint and too far away to be seen with present-day telescopes.
The myriad small faint galaxies from the early universe merged over time into the larger galaxies we can now observe.
That means that over 90% of the galaxies in the universe have yet to be studied! In the near future, the James Webb Space Telescope will be able to study these ultra-faint galaxies and give us more information about their existence.
So back to the question…Why is the sky dark at night if the universe contains an infinity of stars? Researchers came to the conclusion that indeed there actually is such an abundance of galaxies that, in principle, every patch in the sky contains part of a galaxy.
However, starlight from the galaxies is invisible to the human eye and most modern telescopes due to other known factors that reduce visible and ultraviolet light in the universe. Those factors are the reddening of light due to the expansion of space, the universe’s dynamic nature, and the absorption of light by intergalactic dust and gas. All combined, this keeps the night sky dark to our vision.
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Amazing.
On May 25, 2017, the moon photobombed one of our sun-watching satellites by passing directly between the satellite and the sun.
The Solar Dynamics Observatory, or SDO, orbits Earth and watches the sun nearly 24/7 — except when another body, like the moon, gets in the way. These lunar photobombs are called transits, the generic term for when any celestial body passes in front of another.
Transits are one way we detect distant worlds. When a planet in another star system passes in front of its host star, it blocks some of the star’s light so the star appears slightly dimmer. By monitoring changes in a star’s light over time, scientists can deduce the presence of a planet, and even determine what its atmosphere is like. This method has been used to discover thousands of planets, including the TRAPPIST-1 planets.
SDO sees lunar transits about twice a year, and this one lasted about an hour with the moon covering about 89 percent of the sun at the peak of its journey across the sun’s face.
When they’re seen from Earth, we call lunar transits by another name: eclipses.
Solar eclipses are just a special kind of transit where the moon blocks all or part of our view of the sun. Since SDO’s view of the sun was only partially blocked, it saw a partial eclipse. Later this year, on Aug. 21, a total eclipse will be observable from the ground: The moon will completely block the sun’s face in some parts of the US, creating a total solar eclipse on a 70-mile-wide stretch of land, called the path of totality, that runs from Oregon to South Carolina.
Throughout the rest of North America — and even in parts of South America, Africa, Europe and Asia — the moon will partially obscure the sun, creating a partial eclipse. SDO will also witness this partial eclipse.
Total solar eclipses are incredible, cosmic coincidences: The sun is about 400 times wider than the moon, but it also happens to be 400 times farther away, so the sun and moon appear to be the same size in our sky. This allows the moon to completely block the sun when they line up just right.
Within the path of totality, the moon completely obscures the sun’s bright face, revealing the comparatively faint corona — the sun’s pearly-white outer atmosphere.
It’s essential to observe eye safety during an eclipse. You must use proper eclipse glasses or an indirect viewing method when any part of the sun’s surface is exposed, whether during the partial phases of an eclipse, or just on a regular day. If you’re in the path of totality, you may look at the eclipse ONLY during the brief moments of totality.
A total solar eclipse is one of nature’s most awe-inspiring sights, so make your plans now for August 21! You’ll also be able to see the eclipse cross the country that day through the eyes of NASA – including views of the partial eclipse from SDO – on NASA TV and at nasa.gov.
Learn more about the August eclipse — including where, when, and how to safely see it — at eclipse2017.nasa.gov and follow along on Twitter @NASASun.
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The sky may not be falling, but it can certainly seem that way during a meteor shower. Shooting stars, as meteors are sometimes called occur when rock and debris in space fall through the Earth’s atmosphere, leaving a bright trail as they are heated to incandescence by friction with the air. Sometimes the number of meteors in the sky increases dramatically, becoming meteor showers. Some showers occur annually or at regular intervals as the Earth passes through the trail of dusty debris left by a comet. Here’s a guide to the top meteor showers expected in 2017.
At its peak this shower will have about 40 meteors per hour. The parent comet is 2003 EH1, which was discovered in 2003. First quarter moon sets after midnight and meteors radiate from the constellation Bootes.
This shower will have up to 60 meteors per hour at its peak and is produced by dust particles left behind by comet Halley, which has been known and observed since ancient times. The shower runs annually from April 19 to May 28. The waxing gibbous moon will block out many of the fainter meteors this year. Meteors will radiate from the constellation Aquarius.
The annual Perseid shower will have up to 60 meteors per hour at its peak. It is produced by comet Swift-Tuttle. The Perseids are famous for producing a large number of bright meteors. The shower runs annually from July 17 to August 24. The waning gibbous moon will block out many of the fainter meteors this year, but the Perseids are so bright and numerous that it should still be a good show. Meteors will radiate from the constellation Perseus.
This is a minor shower that will produce only about 10 meteors per hour. It is produced by dust grains left behind by comet 21P Giacobini-Zinner, which was first discovered in 1900. The Draconids is an unusual shower in that the best viewing is in the early evening instead of early morning like most other showers. The shower runs annually from October 6-10 and peaks this year on the the night of the 7th. Unfortunately, the nearly full moon will block all but the brightest meteors this year. If you are extremely patient, you may be able to catch a few good ones. Meteors will radiate from the constellation Draco.
The Geminids may be the best shower, producing up to 120 meteors per hour at its peak. It is produced by debris left behind by an asteroid known as 3200 Phaethon, which was discovered in 1982. The shower runs annually from December 7-17. The waning crescent moon will be no match for the Geminids this year. The skies should still be dark enough for an excellent show. Meteors will radiate from the constellation Gemini, but can appear anywhere in the sky.
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Although European Space Agency’s comet-landing mission Rosetta ended on 30 September, the data gathered through it will keep teaching us about comets for a while.
Here are images taken by the Rosetta spacecraft’s camera when Comet 67P/Churyumov–Gerasimenko approached closest to the Sun in August. The comet became very active and outbursts occurred, a typical one thought to release 60–260 tonnes of material in just few minutes!
The outburst can be divided into three categories based on how their dust flow looks like, and the outbursts occurred both when the Sun had started to warm up the previously shaded surface, and after illumination of a few hours. [1] So the outbursts could happen in at least two different ways.
Anyhow, they provide scientists insights of cometary lives and they look pretty cool.
1. Summer fireworks on Rosetta’s comet. 23 September 2016
Copyright: OSIRIS: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM /DASP/IDA; NavCam: ESA/Rosetta/NavCam – CC BY-SA IGO 3.0
Nikola Tesla once paid an overdue hotel bill with a ‘working model’ of his 'death beam’. He warned the staff never to open it, describing it as a war-ending particle weapon that could stop invading armies and make warfare pointless. After his death in 1943, someone finally pried the box open and found nothing but a bunch of harmless old electrical components. Source