“Over the past 30 years, astronomers have gone from zero known extra-solar planets to thousands. Periodic changes in a star’s motion or regular brightness dips give them away. Thanks to these techniques, we’ve revealed the masses and radii of worlds nearby and thousands of light years away. Over 200 are Earth-sized, with many residing in the so-called habitable zone around their stars. Yet with everything we’ve found, there are no potentially habitable Earth-like worlds around Sun-like stars.”
One of the greatest success stories over the past 30 years is the giant leap forward we’ve taken in understanding what worlds lie beyond our Solar System. We’ve gone, in that time, from exactly zero known planets beyond our Solar System to thousands. We’ve found worlds far larger than Jupiter, some of which revolve at distances interior to even Mercury’s orbit. We’ve found planets around blue supergiants and red dwarfs. And we’ve discovered small worlds, some of which are even smaller than Earth. Some of them even occur in the so-called habitable zone of their stars.
Earth precesses around its axis every ~26000 years.
But in addition to this precession, there is an extra wobble that was observed by Kustner and later followed up by Seth Carlo Chandler, Jr called the Chandler Wobble that occurs at a much smaller time scale.
In 1888, Kustner found that the latitude of Berlin had changed slightly
during his observations of the night sky.
Therefore in 1891,Chandler. decided to conduct a 14 month study examining this change. The following is a plot of the spiral path taken by the earth’s axis over that 14 month period.
The following plot shows the motion from 1909 – 2001.
Although many theories indicate that this is due to the fact that earth is not a perfect spherical rigid body, it is still not entirely clear on the mechanism that drives earth into this small wobbly motion.
If you took a closer look at the plots you would find that this wobble is of the order of a couple of meters which most certainly does not seem like a lot.
But if you are an astronomer if you do not account for this correction, you might just end up pointing your telescope at the wrong object
The Sun Will Someday Die, And That’s Why You’re Alive
“It’s true: death comes for us all. It comes for everyone we know and don’t know; it comes for everyone that will ever live. After we’re all dead for billions of years, the Sun will die, too.
But that’s not the full story, and it leaves out the best part. A star’s death brings a remarkable story of cosmic rebirth and possibilities for life to the Universe. It is a story of creation that goes hand-in-hand with destruction, and it follows just below. Give it a shot. It just might be the most remarkable, wonderful story an elementary schoolchild could hope to hear.”
It was a few years ago that I got one of those questions that has stuck in my mind ever since. In particular, it was a message from an elementary school teacher who had a distraught child. The teacher asked me:
“I need a good explanation for a third grader, whose Mom tells me is deeply concerned, that the sun will blow up.”
This is one of the toughest truths about the Universe that many of us will ever learn. The answers to it can make you feel small, inconsequential, and meaningless at times.
For The Last Time: The LHC Will Not Make An Earth-Swallowing Black Hole
“To prevent decay, new, unknown physics — for which no evidence exists — must be invoked.
Even if the newly created black hole were stable, it could not devour the Earth. The maximum rate it could consume matter is 1.1 × 10-25 grams-per-second.
It would take 3 trillion years to grow to a mass of 1 kg.”
Well, it was only a matter of time before someone trotted out the long-debunked claim that the LHC could possibly create an Earth-destroying black hole. I, like most of you, just didn’t expect that person to be the esteemed astronomer Sir Martin Rees!
Well, you’ll be happy to know that not only is his claim untrue, but it’s very easy to demonstrate why. You don’t have to point to cosmic rays (which are more energetic and have struck Earth for billions of years) or rely on anything we haven’t already directly observed. In fact, we can even imagine exotic scenarios that could result in the creation of a black hole, and even then, the Earth is entirely safe.
“All three of these types are notably different from all the other meteorites found on Earth, but have elemental and isotopic commonalities with one another. The ratio of their oxygen isotopes, in particular, were different from that of other meteorites, as well as having younger formation ages. For a long time, scientists suspected they might have a common origin to one another, distinct from the more typical meteorites.
In 1976, the Viking landers returned direct information about the Martian surface, including the Martian atmosphere and the rocks found on the ground. The similarities were striking, leading many to hypothesize that all three types originated from Mars. But the true “smoking gun” came in 1983, when a variety of trapped gases were found in glass formed by the impact of one such shergottite, and it matched the gases found by Viking on Mars.”
Many of us have witnessed meteor showers, bolides, or even randomly large bodies strike the atmosphere of Earth and leave a brilliant streak across the sky. Every once in a while, such a strike will result in an impact on Earth’s surface, leaving a meteorite behind. As of today, over 61,000 meteorites have been discovered, with most of them having huge commonalities of their physical and chemical properties. A few of them, however, are weirdos. They’re younger, they haven’t been in space for very long, and they’re made out of a different mix of materials from the others. For years, it was speculated that they came from Mars, and with the advent of robotic exploration of the surface, we’ve finally found the smoking gun evidence.
Our Sun Is Lighter Than Ever, And The Problem Is Getting Worse
“As time goes on, the amount of mass lost by the Sun will increase, particularly as it enters the giant phase of its life. But even at this relatively steady rate, the growth of helium in the Sun’s core means that we will heat up here on planet Earth. After about 1-to-2 billion years, the Sun will be burning hot enough that Earth’s oceans will boil away entirely, making liquid water impossible on the surface of our planet. As the Sun gets lighter and lighter, it will counterintuitively get hotter and hotter. Our planet has already used up approximately three-quarters of the time we have where Earth is habitable. As the Sun continues to lose mass, humanity and all life on Earth approaches its inevitable fate. Let’s make these last billion-or-so years count.”
As the Sun burns through its nuclear fuel, it loses mass in not one, but two ways. Sure, in its core, it’s fusing hydrogen in a chain reaction into helium, with the reduction in mass corresponding to a gain in energy: the energy that powers the Sun and gives life to all the planets. But it also blows off particles, including electrons, protons, and atomic nuclei, in a phenomenon called the solar wind. Even though more massive stars burn hotter and brighter than less massive ones, the Sun, perhaps paradoxically, will increase in temperature and luminosity as it loses mass to these two processes. The Sun is getting lighter and lighter, and the problem of its increasing energy output will eventually destroy all life on Earth.