• Kilonova Neutron Star Merger pixel-art physics T-shirt, white tee, front view

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Kilonova

GW170817 Neutron Star Merger Physics

\[\Delta t = 1.74 \pm 0.05\ \mathrm{s}\]
$29.99 USD
$29.99 USD
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Size guide S–5XL · inches

Two neutron-star dancers collide in a burst that rains gold. Gravity and light set off together and arrived neck and neck.

The Physics

On 17 Aug 2017 LIGO and Virgo detected gravitational waves from two neutron stars merging about 40 Mpc away. 1.74 ± 0.05 s later, gamma-ray burst GRB 170817A arrived. After a journey of about 130 million years, that tiny gap pins the speed of gravitational waves to the speed of light.

−3 × 10⁻¹⁵ ≤ (v_gw − c)/c ≤ +7 × 10⁻¹⁶

  • v_gw: gravitational-wave speed (m/s)
  • c: speed of light (m/s)
  • 𝓜: chirp mass (kg), measured as 1.188 (+0.004/−0.002) solar masses

The signal arrived on 17 Aug 2017 at 12:41:04 UTC, and multi-messenger astronomy began.

Honest caveat: The 1.74 s gap includes the delay in emitting the gamma rays, which did not leave at the same instant.

On the shirt

Front: Kilonova, the pixel-art character, with the title. Back: the timeline, the speed bound, the chirp mass formula and the start of multi-messenger astronomy. Printed on a unisex tee.

Shipping calculated at checkout by destinationMade to order, ships in 2–5 business days

Details

Size & fitS–5XL

Unisex heavy cotton (Gildan 5000), classic fit.

SizeWidthLengthSleeve
S182815.1
M202916.5
L223018
XL243119.5
2XL263221
3XL283322.4
4XL303423.7
5XL323525

Per avere un'idea: la taglia M è larga 20 in (50.80 cm), circa 3.143 × 1034 lunghezze di Planck (lP = 1.616255 × 10−35 m). Un metro a nastro fa prima.

Measurements in inches, ±1.5 in tolerance.

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Delivery times & where we ship

Returns & replacements21 days

Every item is printed to order, so we can’t accept returns or exchanges for change of mind, or if you ordered the wrong size or colour.

Print defect, misprint, damage or the wrong item? We’ll send a free replacement, or a refund if you prefer. Report it within 21 days of delivery with a photo; no need to send it back.

Full refund & replacement policy

The physics

Two neutron stars spiralled together and merged about 40 megaparsecs away, roughly 130 million light-years. I am the burst they made.

On 17 August 2017 at 12:41:04 UTC, LIGO and Virgo heard the chirp of the inspiral. Its shape gives the chirp mass, 1.188 solar masses. Then, 1.74 ± 0.05 seconds later, Fermi and INTEGRAL caught gamma-ray burst GRB 170817A from the same patch of sky. Gravity and light had raced for about 130 million years and finished almost together.

That tiny gap pins the speed of gravitational waves to the speed of light to within a few parts in 10¹⁵. The gap even includes the delay in launching the gamma rays, which did not leave at the same instant. It was the start of multi-messenger astronomy.

Equations

\[\Delta t = 1.74 \pm 0.05\ \mathrm{s}\]
\[-3\times10^{-15} \le \frac{v_{gw} - c}{c} \le +7\times10^{-16}\]
\[\mathcal{M} = \frac{(m_1 m_2)^{3/5}}{(m_1+m_2)^{1/5}} = 1.188^{+0.004}_{-0.002}\ M_{\odot}\]
SymbolMeaningUnit
\(\Delta t\) delay between the merger signal and the gamma-ray burst \(\mathrm{s}\)
\(v_{gw}\) speed of gravitational waves \(\mathrm{m/s}\)
\(c\) speed of light, 299 792 458 m/s (exact) \(\mathrm{m/s}\)
\(m_1,\ m_2\) masses of the two neutron stars \(\mathrm{kg}\)
\(\mathcal{M}\) chirp mass \(\mathrm{kg}\)
\(M_{\odot}\) solar mass, about 1.989 × 10³⁰ kg \(\mathrm{kg}\)

Sources

  1. LIGO Scientific & Virgo Collaborations (2017) GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral, Phys. Rev. Lett. 119, 161101
  2. LIGO, Virgo, Fermi GBM & INTEGRAL (2017) Gravitational Waves and Gamma-Rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A, Astrophys. J. Lett. 848, L13

Field notes

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