5 Questions You Were Too Embarrassed To Ask About The Expanding Universe
“5.) Are there galaxies moving away faster than the speed of light, and isn’t that forbidden? From our point of view, the space in between us and any distant point is expanding. The farther away something is, the faster it appears to recede from us. Even if the expansion rate were tiny, an object far enough away would eventually cross that threshold of any finite speed, since an expansion rate (a speed-per-distance) multiplied by a great enough distance will give you a speed as fast as you want. But this is okay in General Relativity! The law that nothing can travel faster than the speed of light only applies to an object’s motion through space, not to the expansion of space itself. In reality, the galaxies themselves only move around at speeds that are hundreds or thousands of km/s, much lower than the 300,000 km/s speed limit set by the speed of light. It’s the expansion of the Universe that causes this recession and the redshift, not a true galactic motion.”
The idea that the spatial fabric of the Universe itself is expanding, and that’s what’s behind the observed relationship between redshift and distance has long been controversial, and also long-misunderstood. After all, if more distant objects appear to recede more quickly, couldn’t there be a different explanation, like an explosion that flung many things outward? As it turns out, this isn’t a mere difference in interpretation, there are observations we can make that tell us the answer! The Universe is not expanding ‘into’ anything, despite what your intuition might tell you. The Hubble ‘constant’ isn’t actually a constant, but is rather decreasing as time goes on. The Universe looks like it’s going to expand forever, but even that scientific conclusion is subject to revision depending on what data shows in the future. And although 97% of the galaxies in the Universe are already unreachable, it isn’t a violation of relativity or a faster-than-light phenomenon that’s to blame.
“4.) Voyager’s “Pale Blue Dot” snapshot. On February 14, 1990, after more than a decade of traveling away from Earth and on its way out of the Solar System, the Voyager 1 spacecraft turned its eye back towards home. Looking back at its journey, it was able to take snapshots of six planets, including the above image of Earth, from six billion kilometers away, making this the most distant photo of Earth ever taken.
Although this image was not part of the original mission plan, Carl Sagan’s idea made it to fruition, prompting him to later write the following:
‘That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. […] There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world.’
Voyager 1 is now some 20 billion kilometers distant, as it continues its journey into interstellar space as the most distant spacecraft from Earth.”
It’s no secret that peering out into the distant Universe is best done from space, just as looking at our entire world is best done from that same vantage point. For all of human history until the mid-20th century, this was an utter impossibility. But thanks to advances in rocketry, and how NASA managed to put space technology together, we now have views of everything from our home planet to the deepest recesses of the Universe that have taught us lessons we never could have imagined. From the most distant galaxies to a distant view of Earth, all the way back to the youngest baby picture of the Universe ever taken, NASA has been with us throughout every step of the journey. As we peer ever deeper into the abyss and put not just the cosmic story but our place in it into perspective, it’s important to periodically look back at the beautiful but science-rich images that helped shape our view of what all this is actually about.
When you look at some of these stars, you are looking toward the beginning of time itself. At 13 billion years old, Messier 5 is staggeringly ancient, dating back close to the beginning of the Universe. Messier 5 is a globular cluster consisting of hundreds of thousands of stars bound together by their collective gravity.
This is no normal globular cluster though. At only 25K light years away, it is also one of the biggest clusters known. Incredibly, we can hold wonders like Messier 5 in the palm of our hand thanks to the Hubble Space Telescope.
Messier 5 also presents a puzzle for astronomers. Stars in globular clusters grow old and young together. So Messier 5 should, by now, consist of old, low-mass red giants and other ancient stars. But it is actually teeming with young blue stars known as blue stragglers. These incongruous stars spring to life when stars collide, or rip material from one another.
Our Hubble Space Telescope captured this stunning image of what looks like a soaring, celestial snow angel. This picture shows a bipolar star-forming region, called Sharpless 2-106.
4. Cosmic Holiday Ornament
This festive-looking nearby planetary nebula resembles a glass-blown holiday ornament with a glowing ribbon entwined. This cosmic decoration was spotted by our Hubble Space Telescope.
5. Holiday Lights on the Sun
Even the sun gets festive with it’s festive looking solar flares. This significant flare was seen by our Solar Dynamics Observatory (SOHO) on Dec. 19, 2014. Even though solar flares are powerful bursts of radiation, it cannot pas through Earth’s atmosphere to physically affect humans on the ground. That said, when intense enough, the radiation can disturb the atmosphere in the layer where GPS and communications signals travel.
The universe is expanding even faster than expected
Astronomers using NASA’s Hubble Space Telescope have discovered that the universe is expanding 5 percent to 9 percent faster than expected.
“This surprising finding may be an important clue to understanding those mysterious parts of the universe that make up 95 percent of everything and don’t emit light, such as dark energy, dark matter, and dark radiation,” said study leader and Nobel Laureate Adam Riess of the Space Telescope Science Institute and The Johns Hopkins University, both in Baltimore, Maryland.
The results will appear in an upcoming issue of The Astrophysical Journal.
Fossilized relic discovered by Hubble is a bridge to the Milky Way’s past
“Globular clusters contain stars numbering from tens-of-thousands to tens-of-millions, all within a few hundred light years. Most globulars formed when the Universe was young, with stars over 12 or even 13 billion years old. The Milky Way alone contains around 200 globulars, including Terzan 5. Unlike most globulars, Terzan 5 contains two different populations of stars.”
From 19,000 light years away, Terzan 5 looks a lot like pretty much any globular cluster you’d expect to find: it’s massive, concentrated, with a huge number of stars at right around 12 billion years of age. But mixed in there is a second population of stars just 4.5 billion years old, and tremendously represented in number as well. We’ve never seen a globular like this before, which would have required about 100 million solar masses in gas to remain after the initial burst of formation. But Terzan 5 is an amazing find for containing stars similar to the ones found in the galactic bulge. Is it possible or even probable that this fossilized relic is a survivor of the starbursts that formed the stars in the galactic center, and that it survived them twice?