The Moon is the Earth’s only natural satellite. It is also the fifth-largest natural satellite in the Solar System and the largest among planetary satellites relative to the size of the planet that it orbits. It formed about 4.51 billion years ago from the debris left over after a giant impact between Earth and a Mars-sized body called Theia (this is known as the Giant Impact Hypothesis and is the most widely accepted explanation of the formation of the Moon). This impact happened not long after the Earth has been formed. But, what if that giant impact never happened? What would the Earth without Moon be like?
Continue reading Earth without Moon – what would it be like?Category Archives: Astronomy
Meteorites do not fall to Earth
When a meteoroid hits Earth, it’s not because the space rock has “fallen out of” its orbit. It’s because its orbit crosses over Earth’s orbit at the exact right (or wrong) moment.
Continue reading Meteorites do not fall to Earth
Five space probes leaving the solar system (for now)
As of 2019, only five space probes are leaving the solar system: Pioneer 10, Pioneer 11, Voyager 1, Voyager 2 and New Horizons. The Voyagers already left the solar system and entered the interstellar space (Voyager 1 on August 25, 2012, and Voyager 2 on November 5, 2018. The others also will leave the heliosphere Notes 1 and reach the interstellar space in a few years.
All of these spacecraft are launched by NASA.
Continue reading Five space probes leaving the solar system (for now)
Speed of Light – See how torturously slow it is
The speed of light is the Universal speed limit – nothing can travel faster than light. In the vacuum (commonly denoted c), its exact value is 299,792,458 meters per second (around 186,000 miles per second). In other words, if you could travel at the speed of light, you could go around the Earth 7.5 times in one second.
Continue reading Speed of Light – See how torturously slow it is
There is most probably no Kardashev Type-III civilization in the Universe. Here’s why
In 1964, Russian astrophysicist Nikolai Kardashev (born April 25, 1932) defined three levels of civilizations, based on the order of magnitude of power available to them:
Continue reading There is most probably no Kardashev Type-III civilization in the Universe. Here’s why
Ultima Thule image against a starry background
A beautiful Ultima Thule image, taken by the Long Range Reconnaissance Imager (LORRI) aboard NASA’s New Horizons spacecraft in original context against a starry background (i.e., not zoomed in).
Continue reading Ultima Thule image against a starry background
Watch: 100 Million Stars of the Andromeda Galaxy
In January 2015, NASA released the largest image ever of the Andromeda galaxy, called the Panchromatic Hubble Andromeda Treasury (PHAT), taken by the Hubble telescope. This composite image involved thousands of observations, hundreds of fields, spanned about a third of the galaxy and resolved over 100 million stars.
Totaling 1.5 billion pixels and requiring 4.3 gigabytes of disk space, this photo provides a detailed glimpse at the sheer scale of our nearest galactic neighbor.
Using this gigantic image, filmmaker Dave Achtemichuk created an unforgettable interactive experience.
Continue reading Watch: 100 Million Stars of the Andromeda Galaxy
The sidereal days and axial tilts of the Planets
NASA Goddard Planetary Scientist James O’ Donoghue created a nice animation showing the sidereal days and axial tilts of the solar system planets.
Continue reading The sidereal days and axial tilts of the Planets
Watch: Casting a $20 Million Mirror for the World’s Largest Telescope (Giant Magellan Telescope)
The Giant Magellan Telescope (GMT) is a ground-based extremely large telescope under construction, planned for completion in 2025. When completed, it will be one member of the next class of giant ground-based telescopes that promises to revolutionize our view and understanding of the universe. It will be constructed in the Las Campanas Observatory in Chile.
GMT has a unique design that offers several advantages. It is a segmented mirror telescope that employs seven of today’s largest stiff monolith mirrors as segments. Six off-axis 8.4 meter or 27-foot segments surround a central on-axis segment, forming a single optical surface 24.5 meters, or 80 feet, in diameter with a total collecting area of 368 square meters. The GMT will have a resolving power 10 times greater than the Hubble Space Telescope!
Continue reading Watch: Casting a $20 Million Mirror for the World’s Largest Telescope (Giant Magellan Telescope)
Farout: the most-distant body ever observed in Solar System
Researchers discovered the farthest known object in our solar system and named it “Farout” (far-out-there). It is about 120 times farther than Earth is from the Sun (120 AU Notes 1). For comparison, the most distant planet, Neptune is about 30 AU from the Sun. At its most distant, once upon a time the ninth planet, now a dwarf planet, Pluto, can be 49 AU (7.29 billion km, or 4.53 billion miles) from the Sun. Currently, Pluto is at about 34 AU, making Farout more than three-and-a-half times more distant than the Solar System’s most-famous dwarf planet.
Continue reading Farout: the most-distant body ever observed in Solar System